In order to set a zero position of this kind in the measuring device, calibrated standards or gauge blocks of various design are used. These standards or block gauges, however, are also associated with uncertainties. The uncertainty of a cylindrical ring is specified by the Physikalisch-Technische Bundesanstalt (National Metrology Institute of the Federal Republic of Germany or “PTB” for short) as being 50 nanometres. Gauge blocks of which the uncertainty is specified as being 20 nanometres can also be used. The measurement accuracy is thus always limited to the accuracy of the reference object used to determine the starting position of the probe element of the measuring device. Further measurement inaccuracies are provided by the probe unit itself.
On this basis, the object of the invention can be considered to be that of creating a measuring device and a method which reduce the measurement uncertainty.